Isoniazid resistant tuberculosis in a school outbreak: the protective effect of BCG.

An outbreak of isoniazid resistant tuberculosis occurred in a large second level school. A total of 1,160 teenage pupils were at risk. Nineteen cases of tuberculosis were diagnosed, 15 were students, 9 of whom were among 251 non-vaccinated students and 6 among 909 vaccinated students. Two cases of miliary tuberculosis, one of whom also had tuberculous (TB) meningitis, occurred in the non-vaccinated group. The number of children with Heaf grade +3 or +4 was significantly greater among children who had been given Bacille Calmette-Guérin (BCG) vaccination (8 vs 4.4%). This suggests a boosting effect on the response in vaccinated children. The protective effect of neonatal BCG vaccination in this school outbreak suggests that it provides significant protection against tuberculosis lasting into adolescence.